The birth of the couple’s son on Dec. 14 just happened to be their eldest son Mason’s fifth birthday. The new little bundle of joy also joins sister Penelope Scotland, 2.

The baby’s name has not yet been revealed.

While the proud parents, 35 and 31 respectively, were busy with the baby, auntie Kim Kardashian took the kids to a “Disney On Ice” show to celebrate Mason’s birthday.

“Happy Birthday to the lego master Mason!!! You are so big I can’t take it! You are my everything!!!! I love you so much!!!!” the 34-year-old reality TV queen captioned one selfie with the adorable little man.

A post shared by Kim Kardashian West (@kimkardashian) on Dec 14, 2014 at 10:34am PST

She also posted a photo of the fashionable 5-year-old holding hands with Penelope, Kim’s daughter, North West, and Ciara‘s son, Future Zahir. She shared another photo with all the moms and friends, including makeup artist Joyce Bonelli and Ciara, with their tots.